Abstract : The experimental behavior of superconducting thin-film microbridges, and simple theoretical interpretations of it, are presented for a wide variety of conditions. The most important results concern nonequilibrium aspects of cyclical phase-slip processes observed near Tc, and heating effects observed at low temperatures and high voltages. It is shown experimentally that steps in the I-V curves of long superconducting microbridges near Tc are due to spatially localized voltage units (interpreted as quantum phase-slip centers) which appear at local critical currents determined primarily by variations of Tc along the bridge. Also observed is the ac Josephson effect associated with such centers. (Modified author abstract)